1. Field of the Invention
This invention relates to graphics. In particular, the invention relates to graphic display.
2. Description of Related Art
Rendering a graphic object for display on a display screen is a tedious process. In a typical graphic environment, a graphic controller or a rendering engine is used to accelerate the generation of image. The graphic controller has hardware resources to perform graphic operations at an extremely fast speed. Examples of these graphic operations include line drawing, triangle drawing, shading, block filling, perspective generation, coloring, and graphic transformation (e.g., scaling, rotation, and translation).
The content of a displayed image is typically stored in a frame buffer accessible to the graphic controller. When it is desired to re-generate a previously rendered image, traditional methods typically use a screen capture technique. The screen capture technique involves the transfer of the contents of the frame buffer which corresponds to the displayed image to another temporary storage. This temporary storage is later restored back to the frame buffer to allow the graphic controller to re-display the image.
The screen capture technique suffers a number of drawbacks. First, the process is slow because it requires the transfer of the entire frame buffer. For large images, the time to transfer the graphic data may be prohibitively high. Second, the process requires another buffer memory of the same size as the frame buffer to store the entire graphic data. In applications where processing time and storage requirements are critical, traditional methods using the screen capture technique are not suitable.
Therefore there is a need in the technology to provide a simple and efficient method to re-generate a displayed image.
The present invention is a method and apparatus to re-generate a displayed image. Graphic information is retrieved from a first storage. A graphic controller uses the graphic information to generate the displayed image. The first storage is accessible to a processor and the graphic controller. The graphic information is stored in a second storage which is accessible to the processor. The stored graphic information is retrieved from the second storage. The stored graphic information is written to the first storage to cause the graphic controller to re-generate the displayed image.